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Ecology

Recreating the Intense Conditions of the Earth’s Mantle Solves A Long-standing Geological Mystery

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inner earth

The various layers of the inner Earth. (Credit: Ellen Bronstayn/Shutterstock)

Science is never exactly easy, but it’s especially tough when you can’t see, touch or even really interact with your subject. Consider the plight of a geophysicist interested in the makeup and structure of Earth’s interior. Without being able to dig up a sample of our planet’s ultrahot, ultra-pressurized mantle, how can they figure out what makes our planet work?

The answer, in part, is seismic waves. When the ground shakes, as in an earthquake, the vibrations go through and interact with all the materials in their way. This can provide scientists with a means of imaging all those materials, allowing them to virtually peer beneath the surface.

But sometimes that’s not enough. If the models tell you the vibrations — analogous to sound waves in some cases — should travel at a certain speed, but the data show they don’t, you’re left with an anomaly. Something’s wrong, but without somehow recreating the incredible conditions hundreds of miles below the surface, how can you figure out what?

Just such an issue has been plaguing geophysicists studying the Earth’s innards, who’ve noticed that vibrations from earthquakes traveling through the mantle have been going slower than they should be.

At least until now, that is. According to a Nature paper this week, a team of Japanese scientists figured out what was wrong just by recreating those crazy conditions after all.

Mantle Pieces

Their work all comes down to a specific mineral, calcium silicate (CaSiO3) arranged in what’s called a perovskite structure. Scientists refer to this as calcium silicate perovskite, or simply CaPv. This mineral is a major part of Earth’s mantle, the vast region between surface and the inner core.

The mantle itself is divided into the upper and lower, and the boundary between the two, around 410 miles down, is still somewhat mysterious to scientists. That’s where they’d been finding some of these anomalous velocities for traveling sound waves. One idea was maybe the reason the measurements weren’t lining up with the models was because they didn’t fully understand how the CaPv behaved within the mantle. But it’s hard to know for sure if that’s the case, because in those infernally hot temperatures, CaPv takes on a cubic structure, which breaks down into other forms at temperatures below about 600 kelvin.

As the authors put it, “Despite its importance, no measurements of sound velocities have been made in cubic CaPv at high temperature, because this phase is unquenchable at ambient conditions and hence there is no adequate sample for such measurements.”

So, basically, they just made some.

Mineral Madness

The researchers synthesized some cubic CaPv from a glass rod, and kept it at temperatures up to 1700 K and pressures of up to 23 billion pascal (for reference, standard air pressure is 101,000 pascal). The mineral maintained its cubic form in these extreme conditions, allowing the team to run ultrasonic sound velocity measurements.

They found that the material really doesn’t behave the way the theories had predicted: CaPv is about 26 percent less rigid than expected, so sound waves would in fact travel more slowly through it than expected — just as had been observed.

Not only does the finding resolve the conflict between mantle models and experimental data, but it also supports another intriguing idea: This region between the upper and lower mantle may be home to subducted oceanic crust — parts of the ocean floor forced into the mantle — rife with CaPv.

“These results could contribute to our understanding of the existence and behavior of subducted crust materials in the deep mantle,” the authors write, and they also suggest new research avenues for directly measuring the velocity of seismic waves through mantle materials.

Slowly but surely, scientists are figuring out better ways to look at and understand the invisible depths beneath Earth’s surface.



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Ecology

Whale Sharks, Earth’s Largest Fish, Also Commonly Eat Plants

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whale shark

(Credit: Lindsey Lu/Shutterstock)

Whale sharks, the world’s largest fish, eat significant amounts of plants and algae, scientists reveal in a surprising new study out today in the journal Ecological Monographs.

The sharks aren’t necessarily vegetarians, but they can sometimes go for weeks or month without eating, say researchers from Japan. The vegetative fare may be how the fish fill in their diets when prey is scarce.

“Whale sharks are a globally threatened but very poorly understood species,” said Alex Wyatt, a marine ecologist at the University of Tokyo in Japan, who led the new research. “Despite their massive size… we still know relatively little about them.”

A Whale of A Shark

Whale sharks are indeed massive. The polka-dotted fish can grow up to about 40 feet in length and weigh as much as 47,000 pounds, nearly as much as four African elephants, Earth’s largest land animal, combined. The sharks stick to warm, tropical waters and tend to aggregate in locations where they take can advantage of prime feeding opportunities.

Whale sharks gather in the Gulf of Mexico when fish are spawning, for example, and at Christmas Island in the Indian Ocean the sharks show up in huge numbers during the annual mass spawning of red land crabs. Beyond what they eat at these yearly feasts, though, scientists know little about whale sharks’ diets.

To illuminate the mystery, Wyatt and colleagues tracked stable forms of carbon and nitrogen in the sharks’ tissues, which allowed them to track what and when they’d eaten. The team followed two populations: one group of five captive individuals that were part of the Okinawa Churaumi Aquarium and a second group of eight wild sharks that had become entangled in fishing nets off the coast of Okinawa. The team took blood samples and other measurements of the wild whale sharks as they freed them from the nets. The analysis gave the researchers a picture of the sharks’ overall health, including what they ate and how long it’d been since their last meal.

Diverse Diet

In a surprise find, all of the wild sharks the researchers evaluated had recently eaten some sort of plant matter. What’s more, many of them had experienced a period of prolonged food scarcity in the recent past. The researchers suspect the sharks may fast during long migrations and rely on plants and algae for sustenance when other food is scarce.

“We were able to identify two feeding strategies (oceanic or coastal), evidence of prevalent starvation and the first direct evidence of herbivory by the species,” Wyatt said.

The sharks’ diets fell smack between a pure herbivore and a pure carnivore, the researchers report, meaning whale sharks are actually omnivores. They may not be the only ones. Research from another team recently showed captive bonnethead sharks are able to live off a mostly vegetarian diet of seagrass and squid.

“Omnivory in sharks may be more common than previously recognized,” Wyatt said.



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Ecology

This Robot Dog Teaches Itself New Tricks

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robot dog ANYmal

ANYmal walks like a dog and looks like a dog thanks to its extensive, computerized dog-training courses. (Credit: Hwangbo et al., Sci. Robot. 4, eaau5872 (2019))

Now that’s a headline, right? It’s got a robot dog, plays off a well-known phrase and piques curiosity. Best of all: It’s also accurate! Sort of.

According to a paper today in Science Robotics, an international team of engineers created a way for legged robots — inspired by and physically similar to quadrupedal canines — to use machine learning techniques to learn better ways to move around and adapt to a given environment. As proof, you can watch one such robot “withstanding abuse from their human creators,” as the official caption describes it.

 

Robot Dog Days

Now, I know what you may be thinking: This is dangerously close to that one Black Mirror episode, with the killer robot dogs. Well, as it turns out, it’s actually closer to those other Black Mirror episodes about virtual spaces.

That’s because the “training sessions,” where the dogs did all their learning, took place within a computer. “We introduce a method for training a neural network policy in simulation,” the authors write, “and transferring it to a state-of-the-art legged system, thereby leveraging fast, automated, and cost-effective data generation schemes.” The artificial intelligence — here applied to a specific dog-sized machine named the ANYmal, but the method should work on any machine — learns all its tricks in the digital world, where there are no complicated and expensive parts to engineer and replace, then shows off its abilities in the real world.

Using this technique, the researchers improve on all previous attempts to manipulate such robots, achieving a new level of control and efficiency. In particular, ANYmal can now run up to 25 percent faster than ever, and it recovers from all fall it experienced in real-world testing. (Hence the abuse, above.)

A Robot’s Best Friend

Despite the Black Mirror comparisons, this stuff is more cool and exciting than depressing and unsettling. The authors themselves point out the promise of such mobile technology: “Legged robots may one day rescue people in forests and mountains, climb stairs to carry payloads in construction sites, inspect unstructured underground tunnels, and explore other planets.”

And because the virtual training regimen — all of which took place on simple personal computers and never exceeded 11 hours — was sped up, running about 1,000 times faster than real-time, this method of learning is cheap and gets results relatively quickly.

Of course, other machines will still need their own training sessions for now, and there are other bugs to work out before the technology can achieve those lofty goals. Still, we now have a robot dog that trained themselves to improve their running form and get back up from any kind of a fall — an uplifting and inspirational message that proves just how unlike Black Mirror this really is.



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Ecology

Over 60 Percent of Wild Coffee Species Are at Risk of Extinction

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Coffee beans

(Credit: Ilja Generalov/Shutterstock)

For all those that rely on that cup of coffee to get you going in the morning, here’s another eye-opener: A majority of wild coffee might be going extinct.

That info is courtesy of a new study finding roughly 60 percent of wild coffee species are at risk of going extinct. We don’t drink these wild, unsavory strains often, but they could help our beloved arabica and robusta beans adapt to climate change, resist pests and ward off diseases.

The study on coffee extinction risks, which examined 124 different species, was published today in the journal Science Advances.

Brewed to Perfection

Your poison might be lattes, frappuccinos or macchiatos, but most coffee drinks have one thing in common: their beans. The famous arabica species makes up 60 percent of the world’s traded coffee, with the robusta strain trailing behind at 40 percent. People have been cultivating them for hundreds of years for their smooth, mild taste.

Recent increases in droughts and diseases, though, are putting our beloved beans at risk. But luckily, there are species of wild coffee with hardier traits that allow them to survive in tough conditions. Through interbreeding and hybridization, we could mix wild and domesticated species to create coffee that is both tasty and resilient.

To do that, though, we need to know the prevalence and growth rates of wild breeds. So Aaron P. Davis, a senior research leader at the Royal Botanic Gardens in the United Kingdom, set out to study the extinction risks for all 124 known species of coffee.

Elevated Extinction

With a team of researchers, Davis analyzed over 5,000 data points, coming mostly from species records and field observations. They looked at factors like population decline, deforestation and overall habitat quality. In all, they found that 75 species of wild coffee, or 60 percent, are at risk of extinction. They’ve grown and adapted to life in the wild for centuries, but due to deforestation, their natural habitats and populations continue to dwindle. Habitat loss ranks among the most dire threats to most of the endangered species, the researchers say.

To combat these numbers, and ensure the long-term survival of arabica and robusta, the researchers outline two necessary actions: collect wild strains for hybridization and make sure they’re growing in protected areas, like national parks and nature reserves. But in their research, they found that 45 percent of wild species aren’t being collected and 28 percent aren’t growing in protected areas.

Just because they’re warding off pests, plant diseases and adjusting to climate change, doesn’t mean that they’re immune to extinction. Many wild species are growing sparsely and in limited locations, and if we don’t stockpile and protect them, our precious brews could be at risk. And consequently, our morning-time sanity.



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